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Br J Sports Med. 2018 Mar;52(6):376-384. doi: 10.1136/bjsports-2017-097608. Epub 2017 Jul 11.

A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults.

Author information

1
Department of Kinesiology, McMaster University, Hamilton, Canada.
2
Department of Health Sciences, Lehman College of CUNY, Bronx, New York, USA.
3
Bayesian Bodybuilding, Gorinchem, Netherlands.
4
Sport Performance Research Institute New Zealand, AUT University, Auckland, New Zealand.
5
California State University, Northridge, California, USA.
6
Department of Kinesiology, University of Waterloo, Waterloo, Canada.
7
Health Sciences Library, McMaster University, Hamilton, Canada.
8
Weightology, LLC, Issaquah, Washington, USA.

Abstract

OBJECTIVE:

We performed a systematic review, meta-analysis and meta-regression to determine if dietary protein supplementation augments resistance exercise training (RET)-induced gains in muscle mass and strength.

DATA SOURCES:

A systematic search of Medline, Embase, CINAHL and SportDiscus.

ELIGIBILITY CRITERIA:

Only randomised controlled trials with RET ≥6 weeks in duration and dietary protein supplementation.

DESIGN:

Random-effects meta-analyses and meta-regressions with four a priori determined covariates. Two-phase break point analysis was used to determine the relationship between total protein intake and changes in fat-free mass (FFM).

RESULTS:

Data from 49 studies with 1863 participants showed that dietary protein supplementation significantly (all p<0.05) increased changes (means (95% CI)) in: strength-one-repetition-maximum (2.49 kg (0.64, 4.33)), FFM (0.30 kg (0.09, 0.52)) and muscle size-muscle fibre cross-sectional area (CSA; 310 µm2 (51, 570)) and mid-femur CSA (7.2 mm2 (0.20, 14.30)) during periods of prolonged RET. The impact of protein supplementation on gains in FFM was reduced with increasing age (-0.01 kg (-0.02,-0.00), p=0.002) and was more effective in resistance-trained individuals (0.75 kg (0.09, 1.40), p=0.03). Protein supplementation beyond total protein intakes of 1.62 g/kg/day resulted in no further RET-induced gains in FFM.

SUMMARY/CONCLUSION:

Dietary protein supplementation significantly enhanced changes in muscle strength and size during prolonged RET in healthy adults. Increasing age reduces and training experience increases the efficacy of protein supplementation during RET. With protein supplementation, protein intakes at amounts greater than ~1.6 g/kg/day do not further contribute RET-induced gains in FFM.

KEYWORDS:

growth; hypertrophy; performance. leucine; supplement; whey

PMID:
28698222
PMCID:
PMC5867436
DOI:
10.1136/bjsports-2017-097608
[Indexed for MEDLINE]
Free PMC Article

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